1. Field of the Invention
The present invention concerns a color selection mechanism used in a color cathode ray tube, a frame for use in the color selection mechanism, a cathode ray tube equipped with the color selection mechanism, and a method of manufacturing the frame for use in the color selection mechanism.
2. Description of the Related Art
As a color selection mechanism for use in a color cathode ray tube, for example, there is known a color selection mechanism 51, called xe2x80x9can aperture grill,xe2x80x9d such as that illustrated in FIG. 1. This color selection mechanism 51 has provided therein a frame 56 for use in a color selection mechanism, whose skeletal structure is shaped like a framework, and which is hereinafter referred to simply as xe2x80x9ca framexe2x80x9d. The frame 56 is composed of a pair of supporting members 52 and 53 that are arrayed in parallel in such a way as to oppose each other and elasticity-imparted members 54 and 55, each of which is bridged over the corresponding ends of the supporting members 52 and 53 (and which sometimes for brevity are hereinafter referred to simply as xe2x80x9celastic membersxe2x80x9d). This frame 56 is constructed in such a form wherein a color sorting electrode thin plate (hereinafter referred to simply as xe2x80x9ca thin platexe2x80x9d) 60, having a large number of slit-like electron beam apertures (hereinafter referred to simply as xe2x80x9caperturesxe2x80x9d 59) in one direction, i.e., in the horizontal direction of the screen, is mounted or bridged over the mutually opposing and parallel arranged supporting members 52 and 53 of the frame 56.
The thin plate 60 is constructed in such a form wherein a large number of small-width and strip-like grid elements 58 each comprising a metal thin sheet are arrayed at prescribed intervals in said one direction; and the apertures 59, each having an opening in the vertical direction of the screen are formed between the mutually adjoining grid elements 58. The thin plate 60 is also constructed in such a form wherein the grid elements 58 are bridged over the supporting members 52 and 53, with some extent of tension being imparted thereto by the elastic members 54 and 55.
In this color selection mechanism 51, in order to prevent the grid elements 58 from being vibrated, damper wires 57 are mounted in the array direction of the grid elements 58, so as to contact with the surface of the thin plate 60. The reference symbol 61 represents damper springs for imparting a tension to the damper wires 57.
In addition, although not illustrated, springs for example are respectively attached to the supporting members 52, 53 and the elastic members 54, 55. Through the intermediary of these springs, the color selection mechanism 51 is fixed to the panel of the body of the cathode ray tube.
The supporting members 52, 53 in the long-side direction of the frame 56 and the elastic members 54, 55 in the short-side direction thereof are connected together by welding. Both of these members are assembled in the form of parallel crosses to thereby construct the frame 56.
FIG. 2 and FIGS. 3A to 3D illustrate the schematic construction of a conventional frame 56 that is used in the color selection mechanism 51 of FIG. 1.
As illustrated in FIGS. 2 and 3A to 3D, the frame 56 is constructed in such a form wherein elemental members that comprise a pair of long-side frame members 52, 53 and a pair of short-side elastic members 54, 55 are assembled together in the form of parallel crosses. These both elemental members are connected together by welding, e.g., Tig welding (arc welding that is performed in the atmosphere of an inert gas by using metal such as tungsten as a welding electrode).
As illustrated in FIG. 3A, each of the supporting members 52, 53 has a substantially L-shaped section, and is formed such that, as illustrated in FIG. 3C, the upper and bottom surfaces of each of these members have a prescribed radius of curvature.
As illustrated in FIG. 3B, each of the elastic members 54, 55 is configured such that an angular member used as the elastic member 54, 55 is bent at the positions near the ends thereof, becoming future joint portions. Each elastic member, as illustrated in FIG. 3D, is formed substantially into a shape of horizontally thrown U. And, the ends of each elastic member 54, 55 are connected to the corresponding one-end bottom surfaces of the supporting members 52, 53 by welding.
Welding is done with respect to four positions, respective left end and right end portions of the upper and lower supporting members 52, 53 in FIG. 2.
And, as illustrated in FIG. 4A an enlarged view of the joint portion and its neighborhood of the elastic member 54, 55, in with four surfaces 65a, 65b, 65c, and 65d corresponding to four sides of the end surface 65, which becomes a future welded portion of the elastic member 54, 55, with one surface 65d being made weld-free. Namely, with this one surface 65d being kept not welded, a clearance is instead formed correspondingly thereto. And welding is done with respect to the remaining three surfaces 65a, 65b, and 65c. 
For example, as with the welded range and the welding direction illustrated in FIG. 4B, welding is done with respect to the three surfaces 65a, 65b, and 65c in this order.
As a result of this, in the post-welding state illustrated in FIG. 5, with the clearance remaining at the illustrated portion 66, the inert gas that generates when doing welding has hitherto been removed from this clearance 66.
However, when the clearance 66 that corresponds to the above-described weld-free portion is large, in a thereafter succeeding removing step of oxide scales that have occurred in an annealing step of the frame 56 for use in color selection mechanism, rust of the frame 56, etc., there arises the problem that shot blast balls for use in this removal will be carried through the clearance 66.
For this reason, 100% inspection is visually performed with respect to the entire frame 56 about the entry of the shot blast balls. In a case where shot blast balls remain within the clearance 66, take-out of these shot blast balls is performed. In frame 56 from which shot blast balls have been removed is put into use.
However, even when inspection has been performed with respect to the entire frame 56, by missing shot blast balls during the inspection, it is also possible that shot blast balls will be discovered in the clearance 66 in the course of the thereafter succeeding manufacturing process of the cathode ray tube.
When in this way having formed a cathode ray tube with shot blast balls remaining therein, for example, abnormal discharge may occur due to the shot blast balls when the cathode ray tube is operated. Namely, the shot blast balls contained therein may have serious effects on the withstand voltage characteristic of the cathode ray tube.
Also, it is possible that the rustproofing oil that is used in the rustproofing step will be carried into the clearance 66. Usually, the rustproofing oil that has been carried in comes out from the clearance 66 and vaporizes when performing heat treatment in the annealing step (so-called xe2x80x9cblackeningxe2x80x9d) of the frame.
However, in a case where the clearance 66 is narrow, even when entry of the rustproofing oil occurs, this oil does not come out from the clearance 66 and vaporize during the annealing step. Instead, there may occur a case where this oil comes out when vacuumization is done in the manufacturing step of the cathode ray tube, etc.
On the other hand, in a case where all of the four surfaces 65a, 65b, 65c, and 65d corresponding to the four sides of the end surface 65 of the elastic member 54, 55 have been welded without providing a zone that is made weld-free, no clearance 66 is formed at the side portions of the end surface 65.
When manufacturing the cathode ray tube with this clearance 66 not provided, the welding gas remains between the elastic members 54, 55 and the bottom surfaces of the supporting members 52, 53. As a result, after having manufactured the cathode ray tube, it is possible that during the use thereof the welding gas will ooze out, owing to the aging, from the frame 56 into the body of the cathode ray tube.
As a result of this, the degree of vacuum within the cathode ray tube deteriorates and this has adverse effects on the cathode. It also results from this that the service life of the cathode ray tube becomes short.
In view of the above, the standard of the clearance 66 for degassing is defined as being that a clearance 66 whose size is large enough to enable degassing be ensured; and there be no entry of shot blast balls. However, in the conventional structure, there is the likelihood that the entry of shot blast balls will be missed, and so it becomes necessary to perform 100% inspection. As a result, the productivity of the frame 56 and hence, the cathode ray tube are lowered.
The present invention provides a frame for use in a cathode ray tube, the frame having mounted thereover a thin plate of the cathode ray tube, which frame comprises a pair of mutually opposing supporting members that has fixedly mounted thereover the thin plate, elastic members each bridged over the corresponding ends of the supporting members, and welding gas degassing vent holes that are each formed at a position of the supporting member at which the elastic member is welded thereto.
Also, the present invention has a construction wherein in the frame for use in the cathode ray tube the welding gas degassing vent hole is located almost right above the center of the end surface, becoming a joint portion of the elastic member.
Also, the present invention has a construction wherein in the frame for use in the cathode ray tube the welding gas degassing vent hole is kept closed.
The present invention provides a color selection mechanism of a cathode ray tube, the color selection mechanism having a frame that has mounted thereover a thin plate, which frame comprises a pair of mutually opposing supporting members that has fixedly mounted thereover the thin plate, elastic members each bridged over the corresponding ends of the supporting members, and welding gas degassing vent holes that are each formed at a position of the supporting member at which the elastic member is welded thereto.
The present invention provides a cathode ray tube comprising a color selection mechanism that has a frame having mounted thereover a thin plate, which frame comprises a pair of mutually opposing supporting members that has fixedly mounted thereover the thin plate, elastic members each bridged over the corresponding ends of the supporting members, and welding gas degassing vent holes that are each formed at a position of the supporting member at which the elastic member is welded thereto.
According to the frame of the cathode ray tube, the color selection mechanism of the cathode ray tube, and the construction of the cathode ray tube of the present invention, the welding gas degassing vent hole is formed at the position of the supporting member at which the elastic member is welded thereto. As a result of this, it is not necessary to provide the weld-free portion for degassing the welding gas at the end portion of the elastic member at which the supporting member is welded thereto, i.e., the welding portion thereof. Therefore, even when welding is done with respect to the entire one-full circumference of the end portion, it is possible to sufficiently degas the welding gas so that no welding gas may remain during the manufacturing process of the cathode ray tube or after the manufacture of it.
Also, since there is no need to provide the weld-free portion at the welding portion, no shot blast balls, rustproofing oil, dust, etc. enter from the weld-free portion. It is therefore possible to prevent these shot blast balls, rustproofing oil, dust, etc. from remaining in the frame during the manufacturing process of the cathode ray tube or after the manufacture of it.
The present invention provides a method of manufacturing the frame for use in the cathode ray tube, the method comprising a step of forming the welding gas degassing vent hole at each of the joint portions of the supporting members to the elastic members, a step of welding the elastic members to the supporting members, and a step of closing the welding gas degassing vent hole after the execution of this welding step.
According to the above-described manufacturing method of the present invention, with the welding gas degassing vent hole being formed open, the welding step is performed. It is therefore possible to sufficiently degas the welding gas and thereby prevent the welding gas from oozing out into the cathode ray tube during the manufacturing process of this tube or after complete production thereof.
Also, by closing the welding gas degassing vent hole after the welding step, it is possible to prevent the occurrence of problems such as ooze-out of the welding gas, rustproofing oil, etc., remaining shot blast balls, etc. after the assembly of the cathode ray tube. Therefore it is possible to prevent the occurrence of any defects in the cathode ray tube, such as deterioration of the characteristic, abnormal discharge, and to enhance the quality of the cathode ray tube.
At this time, since shot blast balls cease to remain, it becomes unnecessary to perform 100% inspection with respect to the frame. Therefore, it is possible to increase the productivity of the frame, the color selection mechanism, and the cathode ray tube.